A method is described, for example, in the document: Automatic phase point determination for cardiac CT imaging, Manzke et al., medical imaging 2004, proc. of SPIE vol. 537, 690-699. A proposal is made there that reconstructs the heart volume, on the basis of the ECG signal, in consecutive time intervals, and determines slicewise image correlations in neighboring cardiac phases. If these image correlations are plotted three-dimensionally a z/t-plane (z corresponding to the system axis, t corresponding to the percentage value of the cardiac phases under consideration), the rest phases of the heart are then manifested in this spatiotemporal display as extreme values of the correlation coefficients. Such extreme values can be detected by known computational methods such that the instants of the cardiac phase when the heart is at rest are determined. CT pictures corresponding to these time intervals are then reconstructed from the detector data according to the rest phases thus found.
A complication here is that it is necessary in each case to apply an ECG lead for the CT examination.